1. Field
Apparatuses and methods consistent with exemplary embodiments relate to an audio output apparatus and a display apparatus applying the audio output apparatus, and more particularly, to an audio output apparatus capable of outputting multi-channel audio and a display apparatus applying the same.
2. Description of the Related Art
Due to advancements in flat display panel technology, housing for display apparatuses, such as digital televisions (TVs), is getting slimmer. As display apparatuses become slimmer, various components configuring display apparatuses have been developed for the slimmed display apparatus. When display apparatuses become slimmer, an internal space of the speaker for outputting audio to a front surface of the display apparatus narrows. According to a related art display apparatus, audio is output through a speaker mounted in the display apparatus using a down-firing scheme and a back-firing scheme. A woofer speaker outputting audio in a low-pitched tone band is formed on a back surface of the display apparatus and each of the front speakers outputting audio in a middle-pitched and high-pitched tone band corresponding to a left channel and a right channel is formed at the left and right of a lower area of the display apparatus, respectively. Accordingly, the audio signal output through the woofer speaker is fired through the back surface of the display apparatus and the fired audio signal is diffracted by a back wall and a side wall adjacent to the display apparatus and transferred to the front surface of the display apparatus. Further, the audio signals output through each of the front speakers are fired through a lower surface of the display apparatus and the fired audio signals are diffracted and reflected by the lower surface adjacent to the display apparatus and transferred to the front surface of the display apparatus.
Therefore, a user in front of the display apparatus may listen to the audio output through the woofer speaker and the front speaker.
However, the related art method for outputting audio has disadvantages.
Because the woofer speaker and the front speaker output audio signals in different directions, a difference between a transfer distance of the audio signal output from the woofer speaker to the front surface of the display apparatus and a transfer distance of the audio signal output from the front speaker to the front surface of the display apparatus may occur. Therefore, a phase change in a crossover band in which the audio signals are commonly output in the low-pitched tone band and the middle and high-pitched tone band occurs in an area out of a position which is set in consideration of the distance difference. Therefore, when the user is positioned in the area in which the phase change in the crossover band occurs, the user may experience decreased sound quality when listening to low-quality audio in a section corresponding to the crossover band.
A phase difference between direct sound fired through the woofer speaker and sound reflected from the back wall may occur according to a distance degree between the display apparatus and the back wall. As described above, when the phase difference between the direct sound and the reflected sound occurs, a section in which a specific band needs to be offset and reinforced is changed. Thus, the audio signal in the desired low-pitched tone band may not be generated.
The related art woofer speaker may use a bass reflex enclosure or vented enclosure, to which a Helmholtz resonance scheme is applied, to be able to output the audio signal in which the low-pitched tone band is more reinforced than the related art woofer speaker. That is, the related art woofer speaker synthesizes front sound generated from a woofer unit and back sound reproduced in back of the woofer unit with duct sound amplified by the Helmholtz resonance to be able to output the audio signal in which the low-pitched tone band is reinforced. However, unlike the front sound fired by the back-firing scheme, the duct sound is attenuated by an internal structure configuring the display apparatus and emitted from a clearance of the housing, such that the duct sound is partially lost while being synthesized with the front sound. Therefore, the synthesized sound of the duct sound with the front sound may have a low band loss or noise.
FIG. 1 is a diagram of an operation of outputting an audio signal through a speaker mounted in a related art display apparatus.
As illustrated in FIG. 1, a display apparatus 10 includes a woofer speaker 20 and front speakers 30a and 30b. The woofer speaker 20 is a speaker which is mounted on one side of a back surface of the display apparatus 10 to output an audio signal in a low-pitched tone band applied from the outside. The woofer speaker 20 may include a woofer device 21 which generates acoustic oscillation in connection with the audio signal in the low-pitched tone band which is applied from the outside. Therefore, the woofer speaker 20 fires front sound for the acoustic oscillation generated by the woofer device 21 by a back-firing scheme to output the audio signal in the low-pitched tone band which is applied from the outside. Therefore, the audio signal in the low-pitched tone band output through the woofer speaker 20 is diffracted by a back wall surface adjacent to the display apparatus 10 or the back wall surface and a side wall surface and transferred to a front surface of the display apparatus 10.
Further, the front speakers 30a and 30b are speakers which are each mounted on both sides of a lower surface of the display apparatus 10 to output an audio signal in a middle and high-pitched tone band which is applied from the outside. The front speaker (hereinafter, referred to as a first front speaker) 30a is mounted in a left area of the lower surface of the display apparatus 10 to output a left audio signal in a middle and high-pitched tone band. The other front speaker (hereinafter, referred to as a second front speaker) 30b is mounted in a right area of the lower surface of the display apparatus 10 to output a right audio signal in a middle and high-pitched tone band. As such, the first and second front speakers 30a and 30b, which are mounted at the left and right of the lower surface of the display apparatus 10, output the left and right audio signals in the middle and high-pitched tone band by a down-firing scheme. Therefore, the left and right audio signals in the middle and high-pitched tone band output through the first and second front speakers 30a and 30b are each diffracted by the lower surface adjacent to the display apparatus 10 and transferred to the front surface of the display apparatus 10.
As such, the display apparatus 10 outputs the audio signals in the low-pitched tone band and the middle and high-pitched tone band through the woofer speaker 20 and the first and second front speakers 30a and 30b. Therefore, a user may enjoy high-quality audio sound. However, the audio signals in the low-pitched tone band and the middle and high-pitched tone band output through the woofer speaker 20 and the first and second front speakers 30a and 30b in the display apparatus 10 have a phase difference in a specific band according to a listening position of the user. Thus, a sound quality of audio in the specific band may deteriorate.
As described above, the woofer speaker 20 is mounted on one side of the back surface of the display apparatus 10 to output the audio signal by the back-firing scheme and the first and second front speakers 30a and 30b are each mounted in the left and right areas of the lower surface of the display apparatus 10 to output the audio signal by the down-firing scheme. Therefore, a distance difference may occur between a transfer distance of the audio signal output from the woofer speaker 20 to the front surface of the display apparatus 10 and a transfer distance of the audio signals output from the first and second front speakers 30a and 30b to the front surface of the display apparatus 10. A frequency response in the specific band may be changed according to the listening position of the user due to the distance difference. Here, the specific band is a section in which the audio signals are commonly output in the low-pitched tone band and the middle and high-pitched tone band. The specific band in which the audio signals are commonly output in the low-pitched tone band and the middle and high-pitched tone band is referred to as a crossover (X-over) band. For example, when a phase difference of both ends of the X-band is set to be 0 degrees, the corresponding band is filled due to constructive interference. Further, when the phase difference of both ends of the X-band is set to be 180 degrees, the corresponding band has a deep dip due to destructive interference. The related display apparatus 10 is subjected to parametric equalizer (PEQ) tuning so that the phase difference of the section in which the X-band in a band between the woofer speaker 20 and the first and second front speakers 30a and 30b based on a center of a screen is set to be 0 degrees. However, in the case of tuning the display apparatus 10 by the related art scheme, when the listening position of the user is at the left or right of the display apparatus 10, a phase change of the X-band occurs. Thus, the user at the left or right of the display apparatus 10 has decreased sound quality when listening to low-quality audio in the section corresponding to the X-band.
Further, the audio signal in the low-pitched tone band output through the woofer speaker 20 in the display apparatus 10 is transferred to the front surface of the display apparatus 10, while being diffracted by synthesis of direct sound fired through the woofer speaker 20 with sound reflected by a back wall. In this case, a phase difference between the direct sound fired through the woofer speaker 20 and the sound reflected from the back wall may occur according to a distance degree between the display apparatus 10 and the back wall. When the phase difference between the direct sound and the reflected sound occurs, the section in which the specific band needs to be offset and reinforced is changed. Thus, the desired audio signal in the low-pitched tone band may not be generated.
FIG. 2 is another diagram of the operation of outputting the audio signal through the speaker mounted in a related art display apparatus.
As illustrated in FIG. 2, the display apparatus 10 includes the woofer speaker 20 and the first and second front speakers 30a and 30b. As described above, the front speaker 30a is mounted in the left area of the lower surface of the display apparatus 10 to output the left audio signal in the middle and high-pitched tone band and the second front speaker 30b is mounted in the right area of the lower surface of the display apparatus 10 to output the right audio signal in the middle and high-pitched tone band. As such, the first and second front speakers 30a and 30b, which are mounted at the left and right of the lower surface of the display apparatus 10, output the left and right audio signals in the middle and high-pitched tone band by the down-firing scheme. Therefore, the left and right audio signals in the middle and high-pitched tone band output through the first and second front speakers 30a and 30b are each diffracted by the lower surface adjacent to the display apparatus 10 and transferred to the front surface of the display apparatus 10.
Further, the woofer speaker 20 is a speaker which is mounted on one side of the back surface of the display apparatus 10 to output the audio signal in the low-pitched tone band applied from the outside. In this case, the woofer speaker 20 may output the audio signal in which the low-pitched tone band is more reinforced than the woofer speaker 20 described with reference to FIG. 1 using the Helmholtz resonance scheme. To this end, the woofer speaker 20 may include the woofer device 21 and a duct 23. The woofer device 21 generates the acoustic oscillation in connection with the audio signal in the low-pitched tone band which is applied from the outside. Further, the duct 23 again inverts back sound having an antiphase reproduced in back of the woofer device 21 as much as 180 degrees in a band which is equal to or more than a resonance frequency to fire duct sound in which the low-pitched tone band is reinforced.
Therefore, the woofer speaker 20 fires the synthesized sound of the front sound for the acoustic oscillation generated from the woofer device 21 with duct sound fired from the duct 23 by the back-firing scheme to be able to output the audio signal in which the low-pitched tone band is reinforced.
The duct sound synthesized with the front sound for the acoustic oscillation generated from the woofer device 21 is not synthesized with the front sound through a separate path but is emitted between a clearance of the housing configuring the display apparatus 10 and synthesized with the front sound. Therefore, the duct sound is partially lost while being synthesized with the front sound. Thus, a low band loss and noise of the audio signal output through the woofer speaker 20 may be generated.